Method and apparatus for making tubing from metal tape

ABSTRACT

Thin metal tape or strip is longitudinally folded into tubular form by means of a conical die with conical mandrel. The tape or strip is slightly bent temporarily just prior to folding so that the resulting convex side of the tape or strip becomes the inner tube surface. The tube is formed to have radial tabs which are trimmed and welded. The resulting tube is consistently impervious to fluid.

United States Patent [191 Muller METHOD AND APPARATUS FOR MAKING TUBING FROM METAL TAPE [75] Inventor: Kurt Muller, Hannover, Germany [73] Assignee: Kabel-und Metallwerke Gutehoffnungshutte Aktiengesells ehaft, Hannover,

Germany [22] Filed: Aug. 14, 1972 [21] Appl. No.: 280,483

[30] Foreign Application Priority Data Aug. 16, 1971 Germany 2140945 [51] Int. Cl B211 11/00 [58] Field of Search 72/177, 129, 130, 52, 176, 72/183, 178, 368, 370, 481; 29/477, 477.7

[ June 4,1974

[56] References Cited UNlTED STATES PATENTS 469,663 2/1892 Greenfield 29/477.7

2,574,509 11/1951 Stuart 72/177 2,821,348 1/1958 Langen 72/481 3,474,522 10/1969 Rowell 29/477] Primary ExaminerCharles W. Lanham Assistant Examiner-Robert M. Rogers Attorney, Agent, or FirmRalf H. Siegemund [57] ABSTRACT Thin metal tape or strip is longitudinally folded into tubular form by means of a conical die with conical mandrel. The tape or strip is slightly bent temporarily just prior to folding so that the resulting convex side of the tape or strip becomes the inner tube surface. The tube is formed to have radial tabs which are trimmed and welded. The resulting tube is consistently impervious to fluid.

15 Claims, 6 Drawing Figures 1 METHOD AND APPARATUS FOR MAKING TUBING FROM METAL TAPE BACKGROUND OF THE INVENTION The present invention relates-to improvements in forming and shaping a longitudinally paid metal tape into tubular form with radial tabs formed from the edges of the tape. Metal tape or strip used as stock has thickness not exceeding 0.3 millimeters and theraglial tabs have adjoining disposition so that they can be welded or soldered for closing the tube.

Electrical cables are known to have a core which is enveloped in a tubular sheathing. The sheathing is constructed in that the cable core is enveloped in longitudinally paid-in metal tape or strip having wall thickness not exceeding 0.3 millimeters and having width larger than the circumference of the resulting tube. Radially.

extending tabs are formed from marginal portions of the tape or strip, which tabs run parallel to the axis of tube and cable core. The two tabs are placed in face to face contact, trimmed and welded or soldered in order to provide a fluid-impervious envelope for the cable (see, e.g., US. Pat. No. 3,576,939). Such a cable envelope is particularly impervious to water vapor and provides continuous electrical conductivity about the circumference of the cable, so that the cable conductors are adequately shielded.

Thin metal tape or strip which has been formed into a tube with a tab produced in the manner outlined above, has also been used as conduit for hot or cold fluids. Such tubes are very flexible and can readily be reeled on drums and unwound therefrom without kinking, rupture or the like. Moreover, such tubes are quite light.

However, it was found that the manufacture of tubing with thin walls is not always simple. This is particularly so if the metal strip consists of a light metal, such as aluminum. Aluminum strip or tape which has thickness of not more than 0.3 millimeters is very difficult to work in a continuous process. For example, upon guiding thin strip at its edges, it was found that guide rolls may accidentally bend the edges or even bead them. Unfortunately, a tape which has been deformed in this manner, is no longer suitable for the contemplated tube and tab forming and welding process; undeformed stock is needed for obtaining a tube that is closed along its extension with certainty.

DESCRIPTION OF THE INVENTION It is an object ofthe present invention to provide an improvement in the known methods for forming a tube from longitudinally paid-in metal strips with radially outwardly extending tabs, and welding or soldering the tabs. In accordance with the preferred embodiment of the present invention, it is suggested that the continuously paid in tape or strip runs over a drum or the like for changing direction of travel just prior to folding the tape or strip into tubular form. Particularly, the tape or strip is slightly bent under tension so that the one side of the strip or tape, which will become the inner surface of the tube, is convexly' bent on an axis-which extends transversely to the axis of the tube to be made. It was found that upon guiding the thin metal tape or strip under tension over and against a curved surface, the tape or strip edges are actually stabilized in that undesired beading, Hanging or the like is avoided with certainty. It is essential that the tape runs under tension to some extent as only then will the metal tape stabilize for'the following tab and tube forming process. The tube and tab forming process is followed by trimming so that the two tabs have the same radial extension and offer clean edge surfaces to the subsequent welding or soldering process. That process will yield a consistently closed seam, as the tabs do not deviate locally from the desired and needed configuration.

In order to practice the present invention, it is suggested to deflect or bend the tape or strip by means of a cylindrical guide element in form of a wide roll or a drum shaped body made of plastic with a smooth surface, such as polyethylene and carrying rings which are preferably also made of polyethylene; The rings should be adjustable in axial direction so as to limit severely the freedom of lateral displacement; thus, the rings should be only spaced apart for a distance about equal to the width of the tape. This guide and deflection member is preferably also adjustable as to height in order to accommodate the apparatus to the particularly required tube diameter. The tape or strip is usually advanced to the tube forming tool in horizontal direction, and a tube is usually formed by laterally bending and folding the tape or strip up and about a horizontal axis. The tape or strip is first run over a roll for changing direction in ascending direction, and a second roll turns the tape or strip brackinto the horizontal thereby imparting temporarily convexity to the tape or strip as to the one surface that will become the inner surface of the tube shortly thereafter. The two rolls are preferably mounted on a swivel. This way, the equipment can readily be matched to the requirements posed by making tubes of different diameters.

Upon forming tape,.foil strip or the like into tubular form or a tubular profile, it is of advantage to support the thin stock during the entire forming process, from the outside and, if possible, also from the inside, so as to control each step of the forming process and to avoid undesired deformation. For this particular purpose, it is suggested to provide a tape forming die element which acts on the tape from what will be the outside of the tube. This tool is constructed to have an internal conical surface and is open at the top. A convex/conical mandrel is received in the said conical die, serving therein as coacting die member around which the strip or tape is folded. The mandrel has an upright, longitudinally extending fin. All parts of this tool, which come into sliding contact with the metal tape or strip, are

cerned, so that a longitudinally paid-in aluminum foil is formed into tubular fonn. Tapeportions along the two edges of the tape are shaped to stand up and in parallel to each other as well as in radially outwardly extending position. Moreover, the thusly formed tabs face each other and can be welded to form an integral tab.

In order to practice the present invention, it was found to be advantageous to observe particular geometric relations. The ratio of the diameter of the tube to be made to the length of the conical contour of the tool and die elements is to be about 1:30. This way, it is possible to provide for the making of tubes of various diameters as well as tape (tube wall) thickness without kinking or the like.

The tube shaping mandrel and internal die member of the conical tool is preferably disposed therein for easy longitudinal displacement so that the tooling or parts thereof can readily be changed. Such change may be necessary, because there is, of course, some wear on several parts. The mandrel may be constructed as a solid element particularly if the tube to be made is to be used as conduit for fluids. On the other hand, the tube may have to be formed as an envelope about a cable core. For this case, the mandrel is provided with an axial, concentric bore. The cable core runs through that bore, parallel to the paid-in strip or tape which is formed and folded as tubular envelope about the cable core.

In order to make sure that the welding process of the tape will lead to a satisfactory welding seam, it has to be considered that the strip material may readily oxidize as far as any exposed surface is concerned. Therefore, it is necessary to prepare the edges to be welded so that there is no oxide present which can interfere with the welding process. It is, therefore, necessary or at least advisable, to run the tube with upstanding tabs through a roller cutter for trimming the tab edges. The cutter is comprised of a pair horizontally rotating discshaped cutters cooperating with a guide disc situated immediately opposite one of the cutter as far as the cut- I ting plane is concerned; the guide disc is concentric to the other cutter and is eccentrically displaceable, so that the cutting tool can be adjusted to a variety of strip and tape thicknesses.

The cutting tool must be constructed so that the two mutually facing tabs are trimmed in a clean cut. The cutter, which is located opposite the guide disc, is particularly journalled for the same purpose; its bearings are also displaceably mounted so that the position for the cutter can also be adjusted in accordance with required tape or strip thickness.

In accordance with another feature of the present invention, it was found advisable to wet at least one of the cutters with a suitable liquid, preferably a liquid on alcohol basis. The wetting medium prevents cold welding of the cutter edges with the passing aluminum tape.

} The cutter is preferably wetted in that felt pads slide across the rotating cutters, which felt pads may be drenched in alcohol, and suitable pipes feed wetting material to the felt pads to keep them moist, particularly in the respective areas of contact with the tabs to be cut.

It will be observed that the tube as it leaves the forming and shaping tool, is provided with two tabs, which face each other, but are notyet joined. In order to avoid undue deformation, these two tab portions are to be maintained in position until the welding station has been reached. Therefore, it was found to be advisable to apply some pressure to the tabs, to be effective immediately behind the cutter. Pressure rolls fix, so to speak, the two tabs in mutual position.

In accordance with another feature of the present invention, a guide is provided which is open at the top and guiding the tube generally in the range and area of the cutting station. It is advisable to hold the tabs together right at and through the opening of the guide. This may be necessary in order to compensate for loss in material in the heating zone of the welding station. The clamping and guiding arrangement should be provided with a cover to serve as a heat shield against the arc in the welding station.

While the specification concludes with claims particularly pointingout and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection wht the accompanying drawings in which:

FIG. I is a top view of a tube forming tool proper and of a tab trimmer including features in accordance with the preferred embodiment of the present invention;

FIG. la illustrates a front view of the inner die member in the tube forming tool of FIG. 1;

FIG. lb illustrates a side elevation of the particular member shown in FIG. la;

FIG. 2 is a front view of a roll or drum element for convexly bending metal strip just before being folded for making a tube;

FIG. 3 is a side elevation of a tape or strip guiding device to be disposed immediately ahead of the tube forming tool and including the roll or drum of FIG. 2; and

FIG. 4 is a section view through a cutter and tab trim mer to be placed immediately behind the tube forming tool but ahead of the welding station.

DESCRIPTION OF THE DRAWINGS Proceeding now to the detailed description of the drawings, all of the various figures illustrate equipment cooperating for shaping longitudinal paid metal tape or strip 4 into tubular form with a radially outwardly extending well defined tab. The tape or strip is preferably under 0.3 millimeters thick. A first tube forming tool or die element 1 is provided with an internally conical contour; tool 1 is open at the top. Mandrel 2 or the like is provided inside of tool I. This internal die member 2 has also conical configuration and an upstanding fin 3 which tapers towards the narrow end of the tools conicity. Die member 2 may be hollow so that a cable core may pass through for forming a tube about that core.

Aluminum tape 4 is paid into the tooland it runs into the space between the concavely conical die element l and the conical insert and die member 2, and a tube is formed through gradual folding of the tape in abutment with the internal taper of die 1. The dimension and orientation of the tape is selected so that tape portions along theedges are bent up, at and along fin 3 to form two adjoining radial tabs. Due to the fact that the tool has conical configurations, the material, i.e. the tape, is drawnunder tension as it is being deformed.

The resulting tube with upstanding tabs runs into a tubular guide 5 made preferably from polyethylene and having a slot so that the tabs can pass through. That guide 5 defines the location for a cutting station 6 having two rotary cutters. Cutter 6 trims the tabs and thereby prepares the tabs for the welding step as de scribed, e.g., in US. Pat. No. 3,576,939; followed possibly by folding the tab down as is also described in that patent. Prior to welding the tabs may be squeezed together through rolls (not shown) which are laterally adjustable as well as adjusted for height to keep the two abutting tabs in-position until being welded.

In order to conduct the tape shaping and tube forming process as described properly, and particularly in order to process thin foil, strip or tapes made of light metal such as aluminum, it is suggested to run the tape or' the like across a cylindrical guide member which bends the tape so that the surface thereof becomes convexly pretensioned which will face the interior of the tube.

Guide member 7 is constructed as a drum or rollerlike plastic body with flange rings 8 and 9. These rings 8 and g are displaceably mounted on drum or roll 7 for adjusting an axial space on the drum 7 inbetween.

Thus, the distance between the two flanges or rings 8- and 9 is adjusted to about the width of the tape or strip. This drum 7 is disposed immediately in front of the tape shaping tool of H6. 1 and stabilizes the tape edges.

The tape or strip is only partially wrapped around drum 7, whereby the particular surface of the tape or strip which is in (concave) abutment with the convex drum; is that surface which will be in convex abutment with the concave conical contour of die l during the tube forming process. The drum 7 has disposition so that its axis runs transversely to the axis of the tube to be made; this axis of the drum 7 is the axis of the resulting temporary convexity of that surface of the tape 4 which will face the interior of the tube when made.

This configuration of the guide for the tape tensions the tape against the tube forming process and prevents undue flanging, kinking or beading of the rather sensitive and delicate tape material along the edges. There is an inherent tension in the tape as it runs into the shaping and tube forming tool, and the tension tends to deform the tape opposite to the forming direction of the tube forming process. This was found to be necessary in order to prepare the tape to obtain satisfactory roundness of the tubular configuration as well as uniformly smooth and abutting tabs.

As can be seen from FIG. 3, itis advantageous to combine the tape guide and pretension element 7 with a particular, tape-flow-direction-changing-roll 10. Rolls '7 and B0 are mounted on a swivel which may turn on a pivot point 12. This way, the relative levels of the two rolls 7 and 10 are adjustable, which feature was found to be necessary for matching the tool to different tube diameters. This way, it is no longer necessary to change all of the tooling for processing differently wide and thick tapes or strips. Upon pivoting element 13, the disposition of roll 7 in direction to the tape as it runs off the roll is adjusted.

Turning now to details of FIG. 4, there is illustrated a pair of horizontally extending, rotary cutters l4 and 15, respectively mounted for rotation on vertically journalled shafts l6 and 17. The bearings are not illustrated in detail and the drive for these rotary cutters has been omitted as it is a conventional one. The cutter is mounted somewhat eccentrically as can be determined from an accurate inspection of the Figure. The eccentricity permits matching of the tooling to the various tapes thicknesses as they may arise. Cutter 15 is mounted on a guide disc 18 for particularly guiding the tabs adjacent cutter l4.

The cutter M is also mounted for lateral (radial) displacement by means of an adjusting screw 19 so'that the position of cutter 14 relative to a guide disc 18 can be adjusted accordingly. The outer edge of guide disc 18 is placed somewhat apart from the cutter 14 in order to make sure that the upright standing tab of the tube will not be bent at that point. The rotating elements 18 and 14 are also disposed in particular spatial relation to a slotted guide element 20 for the tube with tabs just made, for running the tube with trimmed tabs exactly as desired to and into the welding station and in proper alignment thereto.

The waste as it is produced by the cutting and tab trimming process is actually a continuous thin strip and may be run out of the system through suitable pickup rolls. The guide member 20 is preferably also made of a suitable plastic such as polyethylene, so that the tube can pass through in smooth gliding contact.

The invention is not limited to the embodiments de scribed above but all changes and modifications thereof not constitutingdepartures from the spirit and scope of the invention are inteded to be included.

I claim:

1. In an apparatus for forming thin metal tape or strip into tubular form with a radial tab, wherein the tape or strip is longitudinally folded about an axis so that one side of the tape or strip becomes the inner surface of a tube, and wherein the edges of the tape or strip are formed into adjoining radial tabs to be trimmed and welded or soldered, the improvement for stabilizing the running tape or strip, comprising:

first means in running engagement with the one side of the tape or strip for deflecting the running tape or strip by slightly bending it temporarily concavely with respect to the one side; and

second means for slightly bending the tape or strip oppositely and under tension as running off straight from the first means, so that the one side of the tape or strip has temporarily convex configuration with respect to a second axis oriented parallel to the first axis and transversely to the axis of folding, the second means being disposed to be effective immediately ahead of the folding of the tape or strip into a tube.

2. In an apparatus as in claim 1, wherein the second means for bending is a cylindrical element over which the tape or strip is partially wrapped for a change in direction of travel.

3. ln an apparatus as in claim 2, wherein the cylindrical element is provided with rings, the tape or strip running in between the rings.

4. In an apparatus as in claim 2, the cylindrical element being disposed for adjustment in direction transversely to the direction of travel of the tape or strip as it runs off the element.

5. in an apparatus as in claim 1, the improvement of a concave conical die element and a convex mandrel as die member, disposed inside said die element for forming the stabilized tape or strip into tubular form, the die element being open at the top, the die member having a tin projecting through the open top of the die element for forming the tabs, the apparatus including a rotating cutter for trimming the tabs.

6. In an apparatus as in claim 5, wherein the conical portion of the die element is about 30 times as long as the tube made has diameter.-

7. in an apparatus as in claim 5, the die member being axiallydisplaceable in the die element.

8. In an apparatus as in claim 5, the die member being hollow. v

9. In an apparatus as in claim 5, the rotating cutter including a pair of cuttingly coacting cutter discs, wherein one cutting disc is on a guide disc, and being radially juxtaposed and facing the other cutting disc of the pair.

10. ln an apparatus as in claim 9, wherein the cutting and guide discs are mounted for mutual radial adjustment to accommodate differently thick tabs.

11. In a method of continuously forming running thin metal tape or strip into tubular form with radial tab, wherein the tape or strip is longitudinally folded about an axis so that one side of the tape or strip becomes the internal surface of a tube and wherein the edges of the tape or strip are formed into adjoining radial tabs which are being trimmed and welded or soldered thereafter, the improvement comprising the steps, immediately preceding the folding step, of slightly deflecting the running tape or strip by slightly bending it concavely with respect to the one side and on a first axis transverse to the direction of running; and immediately thereafter slightly bending the tape or strip under tension so that the one side of the tape or strip has temporarily convex configuration with respect to a second axis of bending oriented transversely to the axis of folding and parallel to the first axis, the second bending step carried out just prior to folding the tape or strip about the axis of folding.

12. In a method as in claim 11, wherein the tape or strip is formed into a tube by a conically shaped die member with conical insert.

13. In a method as in claim 12, wherein the trimming is carried out by means of rotary cutters.

14. In a method as in claim 13, wherein the cutter is being wetted.

15. In a method as in claim 13, wherein a strip as cut off by the cutters is separately reeled after cutolT. 

1. In an apparatus for forming thin metal tape or strip into tubular form with a radial tab, wherein the tape or strip is longitudinally folded about an axis so that one side of the tape or strip becomes the inner surface of a tube, and wherein the edges of the tape or strip are formed into adjoining radial tabs to be trimmed and welded or soldered, the improvement for stabilizing the running tape or strip, comprising: first means in running engagement with the one side of the tape or strip for deflecting the running tape or strip by slightly bending it temporarily concavely with respect to the one side; and second means for slightly bending the tape or strip oppositely and under tension as running off straight from the first means, so that the one side of the tape or strip has temporarily convex configuration with respect to a second axis oriented parallel to the first axis and transversely to the axis of folding, the second means being disposed to be effective immediately ahead of the folding of the tape or strip into a tube.
 2. In an apparatus as in claim 1, wherein the second means for bending is a cylindrical element over which the tape or strip is partiAlly wrapped for a change in direction of travel.
 3. In an apparatus as in claim 2, wherein the cylindrical element is provided with rings, the tape or strip running in between the rings.
 4. In an apparatus as in claim 2, the cylindrical element being disposed for adjustment in direction transversely to the direction of travel of the tape or strip as it runs off the element.
 5. In an apparatus as in claim 1, the improvement of a concave conical die element and a convex mandrel as die member, disposed inside said die element for forming the stabilized tape or strip into tubular form, the die element being open at the top, the die member having a fin projecting through the open top of the die element for forming the tabs, the apparatus including a rotating cutter for trimming the tabs.
 6. In an apparatus as in claim 5, wherein the conical portion of the die element is about 30 times as long as the tube made has diameter.
 7. In an apparatus as in claim 5, the die member being axially displaceable in the die element.
 8. In an apparatus as in claim 5, the die member being hollow.
 9. In an apparatus as in claim 5, the rotating cutter including a pair of cuttingly coacting cutter discs, wherein one cutting disc is on a guide disc, and being radially juxtaposed and facing the other cutting disc of the pair.
 10. In an apparatus as in claim 9, wherein the cutting and guide discs are mounted for mutual radial adjustment to accommodate differently thick tabs.
 11. In a method of continuously forming running thin metal tape or strip into tubular form with radial tab, wherein the tape or strip is longitudinally folded about an axis so that one side of the tape or strip becomes the internal surface of a tube and wherein the edges of the tape or strip are formed into adjoining radial tabs which are being trimmed and welded or soldered thereafter, the improvement comprising the steps, immediately preceding the folding step, of slightly deflecting the running tape or strip by slightly bending it concavely with respect to the one side and on a first axis transverse to the direction of running; and immediately thereafter slightly bending the tape or strip under tension so that the one side of the tape or strip has temporarily convex configuration with respect to a second axis of bending oriented transversely to the axis of folding and parallel to the first axis, the second bending step carried out just prior to folding the tape or strip about the axis of folding.
 12. In a method as in claim 11, wherein the tape or strip is formed into a tube by a conically shaped die member with conical insert.
 13. In a method as in claim 12, wherein the trimming is carried out by means of rotary cutters.
 14. In a method as in claim 13, wherein the cutter is being wetted.
 15. In a method as in claim 13, wherein a strip as cut off by the cutters is separately reeled after cutoff. 